The present invention relates generally to flight conveyors and more particularly to improved drag link chains for moving bulk material along a trough or other conveying surface. The chains are constructed from links having a closed end and an open end.
Links are made by welding, casting or otherwise fixedly securing one piece barrels to first ends of sidebars forming the closed end of a link. A number of links as desired or required are joined together in tandem fashion to form a chain by inserting a pin through a barrel of a closed end of a first link and press fitting the outer ends of the pin in a second end of each sidebar forming the open end portion of the link. The leading side of each link barrel has a flat, vertical surface to act as a pusher of the material being conveyed.
Drag or offset link chains are operated normally with the "open end" of the link facing forward. When a chain is run in this manner, wear is concentrated on both the outer diameter of the pin and the inner diameter of the barrel. If the direction of travel is reversed, and the "closed end" of the links is facing forwardly, there is caused a considerable, undesired amount of concentrated wear resulting from joint articulation between the outer barrel surface of the link and a sprocket tooth.
In the past, a number of attempts have been made to solve the problems encountered and solved by the present invention. In U.S. Pat. No. 581,689 to J. A. Brown, there is shown a chain construction using links wherein apertures are formed that include V-shaped projections for bearing against transverse pins having centrally enlarged portions concave on one side and convex on the other side. Friction between pin and link is presumably minimized by round surface contact of the pin with knife end contact of the projection in the aperture of a link.
U.S. Pat. No. 1,951,764 to F. L. Morse shows a drive chain having links joined together by pins having an arcuate surface on one side and a flat keying surface on the other side. The links rotate about the round side of the pintle but are restrained from turning by the flat side.
U.S. Pat. No. 2,956,442 to C. B. Krekeler shows a mining chain having block links joined together by pintles having a flat side and an arcuate side and further having a cut away, eccentric inner arcuate surface and round outer end portions for fitting in apertures or perforations of the links.
U.S. Pat. No. 3,585,872 to G. S. McDowell is similar to Krekeler U.S. Pat. No. 3,956,442 and shows a cutter chain having cutter bit links and connector links joined together by pintles shaped to provide outer shoulder portions with one side arcuate and the other side flat, an intermediate, cut away portion with an arcuate surface between the flat sided portions of the shoulders.
U.S. Pat. No. 3,880,014 to W. H. Bendall shows a drive chain made from link members serially connected in overlapping relationship so that their connected portions form arcuate rocking bearing surfaces therebetween.
U.S. Pat. No. 4,036,072 to J. F. McKeon shows a steel roller chain wherein bushings, with rollers free to rotate thereabout, are welded between side bars to form a compact structure with no outward projections beyond the outside faces of the side bars, thus reducing overall chain width.